Appraisal of the surgical management for pancreatic serous cystic neoplasms
We read with great interest the paper, “Serous Cyst Adenoma of the Pancreas: Appraisal of Active Surgical Strategy Before It Causes Problems,” by Hwang et al.  published in the June 2012 issue of Surgical Endoscopy. In this article, the authors evaluated their institutional experience with 38 surgically treated serous cystic neoplasms (SCNs) and suggested a potential strategy for managing these lesions.
In summary, before SCNs cause symptoms or grow larger than 5 cm, an active surgical approach, such as minimally invasive surgery, needs to be considered. Most SCNs are found incidentally on cross-sectional imaging performed for other disorders. To date, there have been few data to predict whether an asymptomatic SCN will grow large enough to cause symptoms during the life span of a given patient .
In the paper by Hwang et al. , a linear regression model showed a significant correlation between age and tumor size, indicating, in the authors’ view, that these lesions grow over time and that tumor biology may be different according to the cyst diameter. First, the mean tumor diameter in middle-aged to elderly patients (age, 50–70 years) was slightly greater than in younger patients, indicating a very slow growth. Second, this concept can only be speculated because the linear regression slope does not represent a growth pattern.
Interestingly, the mean tumor diameter in asymptomatic patients was only 3.6 cm, but it was not specified whether in some patients symptoms occurred after a certain follow-up period. Even more surprisingly, five asymptomatic patients younger than 40 years with an SCN 30 mm in size or smaller underwent resection, and it is not clear whether they had truly prophylactic surgery or, for instance, surgery on the basis of cyst morphology.
In fact, the analysis by Hwang et al.  lacks a morphologic classification of SCNs. The classic microcystic adenoma (cluster of cysts smaller than 2 cm forming a honeycomb pattern with a central calcified stellate scar) represents only 35–40 % of all SCNs, which can have variable appearances, from a compactly solid hypervascular to a clearly unilocular cystic pattern. Differentiation between macrocystic SCNs and mucinous tumors is not always possible on cross-sectional imaging and may require measurement of carcinoembryonic antigen in the cyst fluid [3, 4]. This concept is of paramount importance because diagnostic uncertainty represents a clear surgical indication, as already noted in previous reports .
In a specific section of their paper, Hwang et al.  analyze the potential clinical problems derived from SCNs. Apart from the presence of symptoms, size larger than 5 cm represents an issue because “patients with SCNs larger than 5 cm lost the chance to receive minimally invasive surgery (laparoscopic distal pancreatectomy).” According to our experience and the current literature, a tumor diameter greater than 5 cm does not preclude a laparoscopic distal pancreatectomy, which can be safely performed also for larger lesions .
Another potential problem justifying an aggressive approach (prophylactic resection) is possible adhesion to adjacent organs, which was however observed in only two patients with giant lesions (9.5 and 10 cm). In a report of 257 resected SCNs from the Johns Hopkins University, tumors invading surrounding structures (although histologically benign) were defined as “locally aggressive.” The incidence of locally aggressive SCNs was 5.1 % (13/257), but only 0.8 % (2/257) were overtly malignant. They had mean diameter of 10.5 cm.
This large study confirmed that aggressive or malignant SCNs are very rare, and thus prophylactic surgery does not seem to be appropriate . Historically, the generally benign nature of SCNs combined with the morbidity and potential mortality of pancreatic resections has led to a management strategy weighted toward surveillance. Postoperative morbidity still is remarkable. An operative approach for asymptomatic frail or elderly patients may be too risky, and the consequences for loss of pancreatic tissue in young to middle-aged individuals with a long life expectancy are not negligible.
The safety of a periodic surveillance program (rather than an active surgical strategy before SCNs cause problems) was recently appraised by the University of Verona group. In this appraisal, 145 patients with well-documented, asymptomatic SCNs were followed yearly with magnetic resonance imaging (MRI) to estimate the mean tumor growth rate, which was found to be 0.28 cm/year during a median follow-up period of 84 months. The growth curve analysis showed growth acceleration (0.6 cm/year) after 7 years from the baseline evaluation. The macrocystic pattern and personal history of other nonpancreatic tumors were found to be significant predictors of a more rapid mean tumor growth, whereas tumor diameter at the time of diagnosis was not a significant factor .
Taken together, the current evidence does not support the algorithm suggested by Hwang et al. . For the asymptomatic patient, diagnostic uncertainty (morphologic overlap with mucinous neoplasms) seems to be the only indication for resection of small cysts. When a clinical and radiologic diagnosis of SCN has been established, tumor diameter should not be used for decisional purposes (unless the lesion is giant and located in the pancreatic head). When surgery is needed, a tumor diameter greater than 5 cm should not preclude the possibility of a minimally invasive approach.
Giuseppe Malleo, Claudio Bassi, and Roberto Salvia have no conflicts of interest or financial ties to disclose.
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